1. Field of the Invention
The present invention relates to a dye suitable for color resists which are used for the formation of colored pixels, and a method of producing the dye, a radiation-sensitive colored composition using the dye, a color filter using the radiation-sensitive colored composition, a solid-state imaging device, and a liquid crystal display apparatus.
2. Description of the Related Art
Recently, the propagation of digital cameras and camera phones, and the like has resulted in a significantly increased demand for a solid-state imaging device such as a CCD image sensor. As a key device of these displays or optical devices, color filters have been used, and a demand for high sensitivity or miniaturization has been growing further. Such a color filter usually includes a colored pattern of three primary colors of Red (R), Green (G), and Blue (B), and plays a role for decomposing the transmitted light into three primary colors.
Colorants which are used for color filters are required to have the following properties in common. That is to say, colorants are needed, which have preferable optical absorption characteristics in view of color reproducibility; do not have the optical turbulence called heterogeneity of optical density which causes light scattering, color unevenness, and a coarse texture; have a good fastness property, for example heat resistance, light resistance, and the like, under environmental conditions of the production and the usage thereof; and have a high molar extinction coefficient which enables film thinning, and the like.
A pigment dispersion method can be mentioned as one of the methods of manufacturing the aforementioned color filter. A method of manufacturing color filters by photolithography or by inkjet method, using the pigment dispersion method, uses a pigment, and therefore is stable against light or heat. However, since the pigment itself is a particulate, problems termed light scattering, color unevenness, and coarseness frequently arise. To solve these problems, although the refinement into smaller pigment particles has been performed, there is a problem that it is difficult to achieve both the refinement into smaller particles and the dispersion stability.
The methods of manufacturing color filters which can be transformed these pigment dispersion methods include a method using a dye as a coloring material. Since dyes have been dissolved in resists, light scattering, color unevenness, and coarseness as in pigments can be suppressed. Although there was a problem that dyes have a lower heat resistance and light resistance as compared with pigments, recently, dyes having an excellent fastness property have been developed (for example, see JP2008-292970A and JP2010-18788A).
The dyes having an excellent fastness property as mentioned above are mainly synthetic dyes. When synthetic dyes are produced, since halogens are good detachable groups, from the viewpoint of synthesis, synthetic intermediates containing halogens are frequently used. On the other hand, since halogen ions may cause the contamination of the device at the time of producing color filters, the contents thereof need to be controlled in order not to be more than a certain amount. However, there is also a problem that the use of the raw materials not containing halogens leads to raising the level of difficulty of synthesis. For this reason, from the viewpoint of appropriate synthesis, it is preferable that synthetic dyes be produced with the contents of halogen ions being allowed to be not less than a certain amount.
When pigments are produced, reducing the content of a certain ionic impurity in order to manufacture a liquid crystal display element showing an excellent display performance has been studied (for example, see JP1999-194213A (JP-H11-194213A)).